Swiss scientists have discovered why rocking a baby helps get it to sleep. The motion synchronises neural activity in an area of the brain responsible for both sleep patterns and memory retention, according to a study by researchers in western Switzerland.
The findings could be used to treat sleep and memory disorders, say the universities of Geneva and Lausanne and the University Hospital of Geneva (HUG), which carried out the research.
In a controlled test, 18 healthy young adults spent two nights at the HUG Sleep Medicine Centre, once on a swaying bed and the other on a fixed position bed.
Polysomnographic recordings revealed that they enjoyed a longer, deeper sleep when rocked than when they were still, and fell asleep quicker. Continuous rocking helped the brain to synchronize neural activity in the thalamocortico-cortical networks, the study showed.
As this area of the brain is also connected to memory, scientists also conducted memory tests. After a night of swaying, the test subjects were better able to remember pairs of words that they had been given before falling asleep.
Tests on mice also showed a connection to the vestibular system, located in the inner ear, which manages balance and spatial orientation. Mice with non-functioning sensory receptors in the inner ear did not sleep as well, the study found.
“Vestibular sensory stimulation during rocking therefore acts on the neural networks responsible for the specific brain oscillations during sleep,” the scientists said in a statement.
To better identify the specific subcortical structures and neural networks affected by sleep rocking, researchers will now use other techniques, such as optogenetics, to observe and control specific neurons.
“Mapping the communication network between the two systems would make it possible to develop new approaches to treat patients suffering from insomnia, mood disorders, as well as elderly people, who often suffer from sleep and memory disorders,” the team said in a statement.